Respiratory syncytial virus recombinant f protein and vaccine composition containing same

ABSTRACT

The present invention provides a respiratory syncytial virus (RSV) recombinant fusion protein (F protein) in which a polymerization domain derived from a foreign protein is bound to the C terminal of a fusion protein (F protein) lacking a transmembrane domain of a wild-type respiratory syncytial virus (RSV) fusion protein (F protein). The recombinant fusion protein of the present invention is soluble and can retain an F protein trimer. Excellent immune-inducing effects can be expected from the recombinant fusion protein of the present invention, and vaccine composition containing same.

TECHNICAL FIELD

The present application claims priority to Korean Patent Application No. 10-2018-0133084 filed on Nov. 1, 2018 in the Republic of Korea, the disclosures of which are incorporated herein by reference. The present disclosure relates to a fusion protein (F protein) of recombinant respiratory syncytial virus (RSV) and an immunogenic composition containing the same, particularly to a fusion protein (F protein) of recombinant respiratory syncytial virus (RSV), capable of expressing the RSV fusion protein in large quantities and inducing specific neutralizing antibodies, and an immunogenic composition containing the same.

BACKGROUND ART

Respiratory syncytial virus (RSV) is a globally prevalent virus, which causes respiratory diseases and is the major cause of death of children due to severe respiratory infection. Although children are the main target of infection, it is known that it can cause fatal respiratory diseases in patients and the elderly with weak immune functions. Although it is the second cause of respiratory diseases next to influenza, it is known that the annual mortality rate of RSV per 100,000 children below 1 year of age is about 1.3-2.5 times higher than influenza. According to the WHO's report in 2002, 64 million people are infected with RSV each year, and 169,000 out of them die.

For defense against the RSV disease, an inactivated vaccine using inactivated virus was developed at first. However, the use of the inactivated vaccine became impossible due to severe side effects such as aggravation of the symptoms of the disease. There have been efforts to develop a live vaccine, but there are many difficulties in the development because of the metastability and safety problems of the virus. The major antigens of RSV infection are glycoprotein (G protein) and fusion protein (F protein), which are surface proteins. These two proteins are known to play important roles in defense and prevention of viral infection. As the F protein is reported to be more effective in defense against virus, the development of a vaccine using the F protein is being attempted actively. The RSV F protein is an important constituent which fuses with the cell membrane during the early stage of virus entry and is known as the main target of vaccines and antiviral drugs due to high antigenicity. The F protein of RSV is refolded from a “pre-fusion” conformation to a “post-fusion” conformation during entry into a cell.

The F protein consists of about 574 amino acids. The full-length F protein F0 can be divided into F2 (˜20 kDa) and F1 (˜50 kDa) subunits. Three is a furin cleavage site between the subunits F2 and F1, where the protein is cleaved into F2 and F1 by a furin-based protease. In furin cleavage, the amino acid sequences of two sites “RARR” and “KKRKRR” are recognized, where arginine (R) functions as a core amino acid. Heptad repeat regions exist at the N-terminal and C-terminal of the F1 subunit. The heptad repeat region existing at the N-terminal is called HRA, and the heptad repeat region existing at the C-terminal is called HRB. The transformation and cell-virus fusion of the F protein occur as the bent hinge of HRA is spread. In addition, it was found out that trimer formation is induced as the p27 domain is removed by furin cleavage. When the virus comes in contact with a host cell, a harpoon-like structure is put into the cell membrane as the structure of the F protein on the virus surface is changed. Then, the virus is pulled toward the virus, causing the cell membranes to merge. As a result of the fusion, the RNA genome of the virus enters the cell and begins replication. Accordingly, the structural change of the F protein during the fusion process is the key to the understanding of the virus's invasion mechanism. Upon infection by RSV, the F protein is transformed from the pre-fusion conformation to the post-fusion conformation during the process of cell membrane fusion. If the F protein of the virus is transformed to the post-fusion conformation prior to infection (cell fusion), the infectivity is lost.

Due to this characteristic, many researches on stabilizing the F protein in the pre-fusion conformation and increasing the immunogenicity of the F protein are ongoing. When the wild-type F protein is produced as a recombinant protein, it is mostly produced an insoluble form. The insoluble F protein has the problems that purification is difficult, mass expression is impossible because the proper protein structure cannot be formed, and the protein cannot serve as an antigen for inducing immune responses effective for protection against viruses.

Therefore, the inventors of the present disclosure have studied on a novel RSV fusion protein for inducing RSV immune responses, which serves as an antigen capable of inducing RSV immune responses, is easy to purify, and can be easily expressed in large quantities.

DISCLOSURE Technical Problem

The present disclosure is directed to providing a recombinant RSV F protein.

The present disclosure is also directed to providing a soluble recombinant respiratory syncytial virus (RSV) fusion (F) protein having superior immunogenicity-inducing ability.

The present disclosure is also directed to providing a novel method capable of increasing immunogenicity while increasing protein expression level by providing a soluble RSV F protein.

The present disclosure is also directed to providing an RSV immunogen and a method for preparing the same.

The present disclosure is also directed to providing a novel method capable of increasing the antigenicity of an RSV vaccine.

The present disclosure is also directed to providing a soluble RSV F protein, a nucleic acid molecule encoding the same, a composition for inducing immunogenicity, and a use of a soluble RSV F protein for inducing immune responses in animals and human, particularly a use thereof as a vaccine.

Technical Solution Definition of General Terms

Unless defined otherwise in the present disclosure, all the technical terms used to describe the present disclosure have the same meanings as those generally understood by those of ordinary skill in the art to which the present disclosure belongs.

The term “F protein” or “fusion protein” used in the present disclosure refers to a polypeptide or a protein having all or part of the amino acid sequence of the RSV fusion protein. The term “G protein” used in the present disclosure refers to a polypeptide or a protein having all or part of the amino acid sequence of the RSV attachment protein polypeptide. Numerous RSV fusion and attachment proteins are known to those skilled in the art. WO2008/114149 describes exemplary F and G protein variants (e.g., naturally occurring variants) that are publicly available.

The term “protein” or “polypeptide” used in the present disclosure refers to an aggregate of amino acids produced by encoding of specific nucleic acids. Here, the aggregate refers to a unit consisting of two, three, four or more amino acids. The “protein” or “polypeptide” includes not only naturally occurring proteins but also those produced through recombination or synthesis. The term “fragment” refers to a part of a polypeptide (i.e., a subsequence). In general, the arrangement of a polypeptide is represented in a direction of N-terminal→C-terminal defined by the arrangement of the amino and carboxy residues of individual amino acids. The polypeptide is translated from the N (amino)-terminal toward the C (carboxy)-terminal.

The term “recombinant” protein used in the present disclosure refers to a protein encoded by a heterologous (e.g., recombinant) nucleic acid introduced into a host cell, e.g., a bacterial or eukaryotic cell. That is to say, it refers to a protein which has been genetically modified to be produced in large quantities.

The term “domain” of a polypeptide or a protein used in the present disclosure refers to a structurally or functionally defined element in a polypeptide or a protein. For example, a “polymerization domain” is an amino acid sequence in a polypeptide which enhances assembling of monomers into a polymer. For example, the polymerization domain may enhance the assembling to a polymer through association with another polymerization domain (the polymerization domain of an additional polypeptide having the same or different amino acid sequence). The term is also used to refer to a polynucleotide encoding such a peptide or polypeptide. In addition, the polymerization domain may refer to a trimerization domain, which helps the RSV F protein of the present disclosure to be assembled into a trimer.

The term polymerization domain “derived from a heterologous protein” used in the present disclosure is understood to mean a domain derived from species other than RSV virus (e.g., viruses other than the RSV virus, bacteria, bacteriophages, etc.), which helps the RSV F protein in soluble state to be assembled into a trimer.

The term “immunogen” or “antigen” used in the present disclosure is understood to mean any substance having the immunogenicity of inducing or causing immune response in a host cell. For example, it includes such substances as a protein, a peptide or a nucleic acid. Here, the immunogenicity of inducing or causing immune response includes both cellular immunity and humoral immunity. The term “antigen” includes, for example, all or part of a foreign substance that has infiltrated into the body and may be understood to mean all or part of a recombinant RSV F protein. The term induction of immunity by an “antigen” may be understood to mean the formation of an antigen-specific antibody.

The antigen-specific antibody includes a neutralizing antibody which defends a cell from a substance that has infiltrated from outside through neutralization.

The term “vaccine” used in the present disclosure refers to a preparation of an induced antigenic determinant, which is used to induce antibody production or immunity against a pathogen. The vaccine provides immunity against diseases caused by various types of viruses (e.g., influenza, etc.). The term “vaccine” also refers to a suspension or a solution of an immunogen (e.g., modified or mutated RSV F protein) that is administered to a vertebrate to produce protective immunity, i.e., immunity that prevents or reduces the severity of a disease associated with infection. The present disclosure provides a vaccine composition which is immunogenic and can provide protection against a disease associated with infection.

The term “immune response” used in the present disclosure refers to a response of a cell of the immune system, e.g., a B cell, a T cell or a monocyte, in response to stimulus. The immune response may be a B cell response which causes the production of a specific antibody, e.g., an antigen-specific neutralizing antibody. In addition, the immune response may be a T cell response, e.g., a CD4+ response or a CD8+ response. In some cases, the response is specific for a particular antigen (i.e., “antigen-specific response”). When the antigen is derived from a pathogen, the antigen-specific response is a “pathogen-specific response”. A “protective immune response” is an immune response that inhibits the detrimental function or activity of a pathogen, reduces infection by a pathogen, or decreases symptoms (including death) resulting from infection by a pathogen.

Polymerization Domain Derived from Heterologous Protein

As stated above in the definition of general terms, a polymerization domain derived from a heterologous protein is derived from a heterologous species (e.g., virus, bacteria, bacteriophage, etc.) other than the RSV virus, and may refer to a polypeptide domain. In the present disclosure, the polymerization domain is understood to mean a peptide domain which helps the RSV F protein in soluble state to be assembled into a trimer.

The polymerization domain may exist as various forms which can stabilize the protein structure. In a specific exemplary embodiment of the present disclosure, it may be a foldon polymerization domain derived from the bacteriophage T4 fibritin.

The inventors of the present disclosure have identified that binding with the foldon domain may lead to improved trimerization yield. In addition, they have found out that the binding with the foldon domain leads to easier protein purification and increased total antibody titer and neutralizing antibody titer. The inventors of the present disclosure have aimed at remarkably improving trimerization yield by binding the heterologous trimerization domain to the post-fusion F protein.

The foldon domain may be a foldon domain of the fibritin protein of bacteriophage T4. It adopts a β-propeller conformation, and can fold and trimerize in an autonomous way. Although the soluble fusion protein (F protein) with a transmembrane domain removed exists predominantly as monomers, the soluble fusion protein (F protein) with the transmembrane domain removed may be stabilized as trimers by fusing foldon at the C-terminal. The foldon-bound recombinant fusion protein of the present disclosure may exist as a trimeric recombinant fusion protein. As a specific example, the soluble post-fusion F protein with the foldon domain bound may be used as an antigen. The recombinant fusion protein of the present disclosure which exists as a trimer may provide superior neutralizing antibody titer.

In addition, it is expected that the recombinant fusion protein with foldon bound can induce an antibody for a specific major neutralizing epitope as compared to the monomer fusion protein without foldon.

In another exemplary embodiment of the present disclosure, the foldon domain may be linked to the flagellin protein. More specifically, the foldon domain may be linked to the D1 domain of the flagellin protein.

In another exemplary embodiment, the flagellin protein (particularly, the D1 domain of the flagellin protein) may be linked instead of the foldon domain. The D1 domain of the flagellin protein may be a recombinant D1 domain.

The linkage between the foldon domain and the flagellin protein may be achieved, for example, by i) linking the foldon domain first at the C-terminal of the fusion protein (F protein) with the transmembrane domain at amino acids 525-574 of the wild-type respiratory syncytial virus (RSV) fusion protein (F protein) of SEQ ID NO 1 deleted and then linking the D1 domain of the flagellin protein, or ii) linking the foldon domain and the D1 domain of the flagellin protein first and then binding at the C-terminal of the fusion protein (F protein) with the transmembrane domain at amino acids 525-574 of the wild-type respiratory syncytial virus (RSV) fusion protein (F protein) of SEQ ID NO 1 deleted.

Specifically, since flagellin is a protein with very low similarity between bacterial species, its effect may be different depending on which domain of which species is used. For fusion with the recombinant RSV F protein of the present disclosure, it is preferred use the D1 domain of the flagellin protein only. Since the D1 domain includes a TLR5-binding site, it is expected that antigen-specific CD4+ T cell response and strong humoral response will be induced by such mechanisms as NF-kB activation, TLR5-expressing CD11c+ cell stimulation, etc. The flagellin protein is the flagellin protein of Salmonella enterica. Salmonella enterica often exhibits various characteristics such as host specificity, antibiotic resistance, etc. depending on serotype. For example, the flagellin protein encoded by the FliC gene possessed by the serotype group D (Dublin) of Salmonella enterica ssp. enterica may be included in the scope of the present disclosure. In addition, the flagellin protein encoded by the FliC gene possessed by the serotype group D (Dublin) of Salmonella enterica ssp. enterica may be designed newly for use as a recombinant fusion protein. The flagellin D1 domain was designed by linking amino acids 54-176 at the N-terminal of the D1 domain and amino acids 413-454 at the C-terminal with a linker G, and was named as the recombinant D1 domain polypeptide of the flagellin protein (see SEQ ID NO 24). The recombinant D1 domain polypeptide was codon-optimized for easier expression in insect cells (SEQ ID NO 94).

When only the recombinant D1 domain polypeptide is linked, it may be more advantageous in terms of protein expression, trimer structure formation, etc. as compared to when the full flagellin protein is linked because the protein size is decreased and a more compact structure can be formed while maintaining the effect of flagellin.

Preparation of Recombinant Fusion Protein of Respiratory Syncytial Virus

In an exemplary embodiment, the present disclosure provides a new type of recombinant fusion protein with the transmembrane domain of the wild-type respiratory syncytial virus (RSV) fusion protein (F protein) deleted and the fusion protein modified by linking a new domain. Hereinafter, the new type of recombinant fusion protein with the fusion protein modified means a ‘recombinant fusion protein of respiratory syncytial virus’ and is referred to as RFP-RSV (recombinant fusion protein of RSV).

In another exemplary embodiment, the present disclosure provides a new type of recombinant fusion protein with the transmembrane domain of the wild-type respiratory syncytial virus (RSV) fusion protein (F protein) deleted and the amino acid sequence of the fusion peptide domain (FP domain) of the fusion protein (F protein) modified.

In the present disclosure, the respiratory syncytial virus fusion protein (F protein) is distinguished from the wild-type respiratory syncytial virus (RSV) fusion protein (F protein).

The recombinant fusion protein (F protein) of the respiratory syncytial virus (RSV) of the present disclosure means a soluble fusion protein with the transmembrane domain of the wild-type RSV F protein deleted and the amino acid sequence of the fusion peptide domain (FP domain) modified. In an exemplary embodiment, the variation of the amino acid sequence of the fusion peptide domain (FP domain) may occur at the FLGFLLGVG amino acid sequence of the FP domain. Hereinafter, the F protein with the transmembrane domain of the F protein deleted and one or more amino acid substitution induced may be named as sF protein (soluble fusion protein).

The fusion protein of the wild-type respiratory syncytial virus may include SEQ ID NO 1 or an amino acid sequence which is 80%, specifically 85%, more specifically 90%, further more specifically 95%, identical to the sequence of SEQ ID NO 1. In an exemplary embodiment of the present disclosure, the fusion protein with a ‘polymerization domain derived from a heterologous protein’ linked may have the transmembrane domain of the wild-type RSV F protein deleted, and is specifically represented by SEQ ID NO 2. The transmembrane domain may be located at amino acid sequences 525-574.

In an exemplary embodiment of the present disclosure, the fusion protein with a ‘polymerization domain derived from a heterologous protein’ linked may have the transmembrane domain of the wild-type RSV F protein deleted, and may further have the FLGFLLGVG sequence at positions 137-145 of SEQ ID NO 2 modified. The amino acid sequences 137-145 of SEQ ID NO 2 may be included in the fusion peptide domain (FP domain).

In an exemplary embodiment of the present disclosure, the fusion protein with a ‘polymerization domain derived from a heterologous protein’ linked may have the transmembrane domain at amino acid sequences 525-574 of the wild-type RSV F protein deleted, may further have the FLGFLLGVG sequence at positions 137-145 of SEQ ID NO 2 modified, and the FLGFLLGVG sequence may be substituted with i) AAGAAAGAG, ii) QNGQNNGSG, iii) NSGNSSGGG, or iv) TLSKKRKRR. Specifically, the fusion protein may be represented by SEQ ID NO 3, 4, 5 or 6.

In an exemplary embodiment of the present disclosure, the fusion protein with a ‘polymerization domain derived from a heterologous protein’ linked may have the transmembrane domain of the wild-type RSV F protein deleted, and may have one or more amino acid substitution in the amino acid sequence of SEQ ID NO 2. Specifically, the amino acid substitution may occur at one location.

The fusion protein may have amino acid substitution at the following positions of the amino acid sequence of SEQ ID NO 2:

(a) substitution of the amino acid residue F at 140th position with W;

(b) substitution of the amino acid residue E at the 163rd position with Q;

(c) substitution of the amino acid residue V at the 179th position with L;

(d) substitution of the amino acid residue L at the 188th position with Q;

(e) substitution of the amino acid residue T at the 189th position with L;

(f) substitution of the amino acid residue E at the 487th position with L; or

(g) substitution of the amino acid residue F at the 505th position with W.

The above-described substitutions (a)-(g) are preferred because soluble RSV can be obtained through the amino acid substitutions at the specified locations of the amino acid sequence of SEQ ID NO 2.

For example, the sF protein includes, on the basis of SEQ ID NO 2, one or more substitution selected from a group consisting of:

(a) substitution of the amino acid residue F at the 140th position with W (SEQ ID NO 7);

(b) substitution of the amino acid residue E at the 163rd position with Q (SEQ ID NO 8);

(c) substitution of the amino acid residue V at the 179th position with L (SEQ ID NO 9);

(d) substitution of the amino acid residue L at the 188th position with Q (SEQ ID NO 10);

(e) substitution of the amino acid residue T at the 189th position with L (SEQ ID NO 11);

(f) substitution of the amino acid residue E at the 487th position with L (SEQ ID NO 12); and

(g) substitution of the amino acid residue Fat the 505th position with W (SEQ ID NO 13).

In another exemplary embodiment, the sF protein may have, on the basis of SEQ ID NO 2,

the amino acid corresponding to the 140th position substituted with W, and the amino acid corresponding to the 163th position substituted with Q (SEQ ID NO 14);

the amino acid corresponding to the 140th position substituted with W, the amino acid corresponding to the 163th position substituted with Q, the amino acid corresponding to the 188th position substituted with Q, and the amino acid corresponding to the 189th position substituted with L (SEQ ID NO 15);

the amino acid corresponding to the 488th position substituted with W, and the amino acid corresponding to the 163rd position substituted with Q (SEQ ID NO 16);

the amino acid corresponding to the 488th position substituted with W, and the amino acid corresponding to the 179th position substituted with L (SEQ ID NO 17);

the amino acid corresponding to the 140th position substituted with W, and the amino acid corresponding to the 505th position substituted with W (SEQ ID NO 18);

the amino acid corresponding to the 487th position substituted with L, and the amino acid corresponding to the 505th position substituted with W (SEQ ID NO 19);

the amino acid corresponding to the 163rd position substituted with Q, and the amino acid corresponding to the 505th position substituted with W (SEQ ID NO 20);

the amino acid corresponding to the 188th position substituted with Q, the amino acid corresponding to the 189th position substituted with L, and the amino acid corresponding to the 505th position substituted with W (SEQ ID NO 21); or

the amino acid corresponding to the 163rd position substituted with Q, and the amino acid corresponding to the 487th position substituted with L (SEQ ID NO 22).

In an exemplary embodiment of the present disclosure, an RSV F protein with a part of the fusion peptide (F protein) of the wild-type respiratory syncytial virus (RSV) deleted may be represented by SEQ ID NO 2, and the RSV F protein of SEQ ID NO 2 may be provided as an RSV immunogen or an antigen for inducing immunity against RSV.

The inventors of the present disclosure have further found out that excellent neutralizing antibody-inducing ability is achieved when the polypeptide of the foldon domain or the foldon domain-flagellin protein (particularly D1 domain) is further linked.

The RSV F protein of SEQ ID NO 2 includes one with the amino acid sequences 525-574 of the wild-type RSV F protein of SEQ ID NO 1 deleted.

The inventors of the present disclosure have developed through researches for a long period of time a recombinant RSV F protein immunogen capable of providing excellent neutralizing antibody titer through one, two or more sequence variation of the fusion peptide of the RSV F protein.

The RFP-RSV of the present disclosure may be used for prevention, treatment, etc. of RSV infection, and specifically may be provided as a vaccine for prevention of RSV infection.

In an exemplary embodiment, the RFP-RSV of the present disclosure may be prepared by mutating or modifying a part of the sequence of the fusion peptide of the RSV F protein.

The present disclosure is also directed to providing a soluble RSV F polypeptide, a nucleic acid molecule and/or a composition for inducing immunogenicity, and a use of the soluble RSV F protein for inducing immune response in an animal and human body, particularly a sue as a vaccine. The present disclosure also includes, as a specific use as a vaccine, a step of administering an effective amount of a nucleic acid molecule encoding the RSV F polypeptide, a vector including the nucleic acid molecule and/or a polypeptide transcribed from the nucleic acid molecule to a subject. In a specific aspect, the present disclosure relates to a method for inducing a neutralizing anti-respiratory syncytial virus (RSV) F protein antibody in a subject, which includes a step of administering an effective amount of a nucleic acid molecule encoding the RSV F polypeptide, a vector including the nucleic acid molecule and/or a polypeptide transcribed from the nucleic acid molecule to a subject.

In an exemplary embodiment, one or more hydrophobic amino acid at positions 137-145 of the amino acid sequence of SEQ ID NO 2 may be substituted with a hydrophilic amino acid. More specifically, the RSV F protein of SEQ ID NO 2 may have mutation wherein one or more hydrophobic amino acid of the fusion peptide is substituted with a hydrophilic. Further more specifically, in an exemplary embodiment of the present disclosure, the hydrophobic amino acids of the FLGFLLGVG sequence at positions 137-145 of SEQ ID NO 2 may be substituted with A to give AAGAAAGAG and the modified fusion protein (SEQ ID NO 3, FP1) may be linked with a polymerization domain derived form a heterologous protein.

In an exemplary embodiment, one or more polar amino acid at positions 137-145 of the amino acid sequence of SEQ ID NO 2 137-145 may be substituted with a nonpolar amino acid. More specifically, the RSV F protein of SEQ ID NO 2 may have mutation wherein a polar region of the fusion peptide is modified with a nonpolar side chain. Further more specifically, a fusion protein with the FLGFLLGVG sequence at positions 137-145 of SEQ ID NO 2 modified to QNGQNNGSG (SEQ ID NO 4, FP3) may be linked with a polymerization domain derived form a heterologous protein.

In another exemplary embodiment, a fusion protein with the FLGFLLGVG sequence at positions 137-145 of SEQ ID NO 2 modified to NSGNSSGGG (SEQ ID NO 5, FP4) may be linked with a polymerization domain derived form a heterologous protein.

In another exemplary embodiment, a fusion protein with the FLGFLLGVG sequence at positions 137-145 of SEQ ID NO 2 modified to TLSKKRKRR (SEQ ID NO 6, FP6) may be linked with a polymerization domain derived form a heterologous protein.

The polymerization domain derived a heterologous protein may function as an immunogen when linked to the fusion protein. It may improve the stability of the protein structure and may advantageously induce a neutralizing antibody through trimerization.

Although mutation may occur at the amino acid sequence of positions 137-145 of SEQ ID NO 2, the function and effect of the protein may vary greatly depending on the substitution, deletion or insertion of the amino acid constituting the protein as well known to those skilled in the art.

In another exemplary embodiment of the present disclosure, further mutation that stabilizes the F1 domain of the wild-type RSV F protein may be included. The further mutation related with stabilization includes at least one selected from a group consisting of (a)-(g) on the basis of SEQ ID NO 2:

(a) substation of amino acid residue at position 140;

(b) substation of amino acid residue at position 163;

(c) substation of amino acid residue at position 179;

(d) substation of amino acid residue at position 188;

(e) substation of amino acid residue at position 189;

(f) substation of amino acid residue at position 487; and

(g) substation of amino acid residue at position 505.

More specifically, the RSV fusion protein of the present disclosure may have, on the basis of SEQ ID NO 2, one or more amino acid substitution selected from a group consisting of:

(a) substation of amino acid residue F with W at position 140 (SEQ ID NO 7);

(b) substation of amino acid residue E with Q at position 163 (SEQ ID NO 8);

(c) substation of amino acid residue V with L at position 179 (SEQ ID NO 9);

(d) substation of amino acid residue L with Q at position 188 (SEQ ID NO 10);

(e) substation of amino acid residue T with L at position 189 (SEQ ID NO 11);

(f) substation of amino acid residue E with L at position 487 (SEQ ID NO 12); and

(g) substation of amino acid residue F with W at position 505 (SEQ ID NO 13).

The fusion protein may be linked to a polymerization domain derived from a heterologous protein.

In another exemplary embodiment, the fusion protein may be one wherein, the amino acid corresponding to position 140 of SEQ ID NO 2 is substituted with the amino acid W, and the amino acid corresponding to position 163 is substituted with the amino acid Q (SEQ ID NO 14);

the amino acid corresponding to position 140 of SEQ ID NO 2 is substituted with the amino acid W, the amino acid corresponding to position 163 is substituted with the amino acid Q, the amino acid corresponding to position 188 is substituted with the amino acid Q, and the amino acid corresponding to position 189 is substituted with the amino acid L (SEQ ID NO 15);

the amino acid corresponding to position 488 of SEQ ID NO 2 is substituted with the amino acid W, and the amino acid corresponding to position 163 is substituted with the amino acid Q (SEQ ID NO 16);

the amino acid corresponding to position 488 of SEQ ID NO 2 is substituted with the amino acid W, and the amino acid corresponding to position 179 is substituted with the amino acid L (SEQ ID NO 17);

the amino acid corresponding to position 140 of SEQ ID NO 2 is substituted with the amino acid W, and the amino acid corresponding to position 505 is substituted with the amino acid W (SEQ ID NO 18);

the amino acid corresponding to position 487 of SEQ ID NO 2 is substituted with the amino acid L, and the amino acid corresponding to position 505 is substituted with the amino acid W (SEQ ID NO 19);

the amino acid corresponding to position 163 of SEQ ID NO 2 is substituted with the amino acid Q, and the amino acid corresponding to position 505 is substituted with the amino acid W (SEQ ID NO 20);

the amino acid corresponding to position 188 of SEQ ID NO 2 is substituted with the amino acid Q, the amino acid corresponding to position 189 is substituted with the amino acid L, and the amino acid corresponding to position 505 is substituted with the amino acid W (SEQ ID NO 21); or

the amino acid corresponding to position 163 of SEQ ID NO 2 is substituted with the amino acid Q, and the amino acid corresponding to position 487 is substituted with the amino acid L (SEQ ID NO 22).

In an exemplary embodiment, the present disclosure provides an immunogenic composition and/or a vaccine, which contains a recombinant fusion protein of RSV wherein the RSV F protein is linked to a ‘polymerization domain derived from a ‘heterologous protein’.

The wild-type respiratory syncytial virus fusion protein may be selected from the F protein of an RSV A strain, an RSV B strain, an HRSV A strain, an HRSV B strain, an BRSV strain or an avian RSV strain or any variant thereof. In a specific exemplary embodiment, the wild-type F protein polypeptide may be an F protein represented by SEQ ID NO 1, and an F protein which has sequence identity of 80% or higher to SEQ ID NO 1 may also be included in the wild-type RSV of the present disclosure. Numerous additional examples of F protein polypeptides from other RSV strains are disclosed in WO/2008/114149 (which is incorporated herein by reference in its entirety). Additional variants can arise through genetic drift, or can be produced artificially using site-directed or random mutagenesis or by recombination of two or more preexisting variants.

In an exemplary embodiment of the present disclosure, the sF protein may be provided as a recombinant fusion protein (F protein) RSV as being linked to a polymerization domain derived from a heterologous protein at the C-terminal.

The polymerization domain derived a heterologous protein may be a polypeptide, and the polypeptide may be a bacteriophage T4 fibritin foldon domain polypeptide having SEQ ID NO 23.

The foldon domain may be particularly advantageous for trimerization of the sF protein of the present disclosure, and may be excellent in inducing a neutralizing antibody.

The fusion protein to which the polymerization domain derived from a heterologous protein is linked, e.g., an sF protein, may have one or more amino acid sequence selected from SEQ IDS NO 3-22, specifically an amino acid sequence of SEQ ID NO 5. The amino acid of SEQ ID NO 5 may be named FP4. The FP4 exhibits excellent stability and superior neutralizing antibody-inducing ability when a foldon domain or a foldon-flagellin D1 domain is bound.

In another exemplary embodiment, a recombinant D1 domain polypeptide of the flagellin protein having SEQ ID NO 24 may be further linked at the C-terminal of the bacteriophage T4 fibritin foldon domain polypeptide having SEQ ID NO 23. Through this, more improved neutralizing antibody induction may be expected.

In another exemplary embodiment, the RFP-RSV may have the C-terminal of the fusion protein (sF protein) linked to the N-terminal of the polymerization domain derived from a heterologous protein, and the linkage between the fusion protein and the polymerization domain may be covalent bonding by a linker. The linker may have an amino acid sequence of KLSG, and may be called a KLSG linker. In an exemplary embodiment, the RFP-RSV may have the C-terminal of the KLSG linker covalently bonded to the N-terminal of the bacteriophage T4 fibritin foldon domain polypeptide having SEQ ID NO 23. In an exemplary embodiment, the present disclosure may provide RFP-RSV having an amino acid sequence selected from SEQ ID NOS 28-48.

In another exemplary embodiment, the RFP-RSV may have the C-terminal of the bacteriophage T4 fibritin foldon domain polypeptide having SEQ ID NO 23 linked to the recombinant D1 domain polypeptide of the flagellin protein having SEQ ID NO 24 by a GGGS linker having the amino acid sequence of GGGS. In an exemplary embodiment, the recombinant fusion protein of respiratory syncytial virus may have the C-terminal of the fusion protein (F protein) linked to the N-terminal of the bacteriophage T4 fibritin foldon domain polypeptide having SEQ ID NO 23 by a KLSG linker, and the C-terminal of the bacteriophage T4 fibritin foldon domain polypeptide having SEQ ID NO 23 linked to the N-terminal of the recombinant D1 domain polypeptide of the flagellin protein having SEQ ID NO 24 by a GGGS linker. The RFP-RSV may be an RFP-RSV having an amino acid sequence selected from SEQ ID NOS 49-69.

In an exemplary embodiment, the RFP-RSV may have the C-terminal of the sF protein linked to a polymerization domain derived from a heterologous protein by a linker, and the linkage by the linker may be covalent bonding.

In an exemplary embodiment, the recombinant fusion protein may include two or more linkers and two or more polymerization domains derived from heterologous proteins.

For example, the recombinant fusion protein may be roughly described as follows. However, the SK-FP4 described below is only an example of the sF protein provided for illustrative purpose, and the present disclosure is not limited thereto. In addition, the linker 1 and the linker 2 may be the same or different, and the polymerization domain derived from a heterologous protein 1 and 2 may also be the same or different.

-   -   (sF protein)-(linker 1)-(polymerization domain derived from a         heterologous protein 1)     -   (sF protein)-(linker 2)-(polymerization domain derived from a         heterologous protein 2)     -   (sF protein)-(linker 1)-(polymerization domain derived from a         heterologous protein 1)-(linker 3)-(polymerization domain         derived from a heterologous protein 2)

In another exemplary embodiment, the present disclosure may include the following recombinant fusion proteins.

-   -   (sF protein)-(linker 1)-(polymerization domain derived from a         heterologous protein 1)     -   (sF protein)-(linker 2)-(adjuvant domain derived from a         heterologous protein)     -   (sF protein)-(linker 1)-(polymerization domain derived from a         heterologous protein 1)-(linker 2)-(adjuvant domain derived from         a heterologous protein)

For example, the adjuvant domain derived from a heterologous protein may include the flagellin protein and the D1 domain of the flagellin protein.

In an exemplary embodiment of the present disclosure, the linker 1 may be a KLSG linker, the linker 2 may be a KLGGGS linker, and the linker 3 may be a GGGS linker. Specifically, the C-terminal of the KLSG linker may be linked to the N-terminal of the foldon domain, and the C-terminal of the KLGGGS linker may be linked to the D1 domain of flagellin (specifically, the recombinant D1 domain of flagellin). Specifically, the C-terminal of the foldon domain and the N-terminal of the D1 domain of flagellin may be linked by a GGGS linker.

In an exemplary embodiment, the recombinant fusion protein may be provided in the form wherein a KLSG linker or a KLGGGS linker is bound to the C-terminal of the sF protein. Specifically, the KLSG linker may link the sF protein with the foldon domain. The linkage may be formed by covalent bonding. The C-terminal of the sF protein may be linked to the N-terminal of the KLSG linker, and the C-terminal of the KLSG linker may be linked to the N-terminal of the foldon domain. Specifically, the KLGGGS linker may link the sF protein and the D1 domain of flagellin (specifically, the recombinant D1 domain of flagellin). The linkage may be formed by covalent bonding. The C-terminal of the sF protein may be linked to the N-terminal of the KLSG linker, and the C-terminal of the KLSG linker may be linked to the N-terminal of the D1 domain of flagellin (specifically, the recombinant D1 domain of flagellin).

In an exemplary embodiment, when the sF protein is linked to the polymerization domain derived from a heterologous protein by a linker in the recombinant fusion protein, the C-terminal of the linker having the amino acid sequence KLSG may be covalently bonded to the N-terminal of the bacteriophage T4 fibritin foldon domain having SEQ ID NO 23.

In another exemplary embodiment, the present disclosure provides an RFP-RSV wherein the recombinant D1 domain polypeptide of the flagellin protein having SEQ ID NO 24 is linked to the C-terminal of the fusion protein (F protein) with the transmembrane domain at amino acids 525-574 of the wild-type respiratory syncytial virus (RSV) fusion protein (F protein) of SEQ ID NO 1 deleted. The amino acid sequence of the fusion protein (F protein) with the transmembrane domain at amino acids 525-574 of the wild-type respiratory syncytial virus (RSV) fusion protein (F protein) of SEQ ID NO 1 deleted may be represented by SEQ ID NO 2. In another exemplary embodiment, the present disclosure may provide an RFP-RSV wherein the C-terminal of an amino acid sequence represented by SEQ ID NOS 3-22 is covalent bonded to a recombinant D1 domain polypeptide of the flagellin protein (SEQ ID NO 24) by a KLGGGS linker. The RFP-RSV may be represented by an amino acid sequence selected from SEQ ID NOS 70-90.

In another exemplary embodiment, the present disclosure may provide a nucleic acid encoding the RFP-RSV. The recombinant fusion protein may be used as an RSV antigen, and the present disclosure may provide a recombinant nucleic acid encoding the antigen.

In a specific exemplary embodiment, the recombinant nucleic acid is codon-optimized to be expressed in a selected prokaryotic or eukaryotic host cell. As a non-limiting example, the recombinant fusion protein may have an amino acid sequence selected from SEQ ID NOS 28-90. The nucleic acid may be introduced into a prokaryotic or eukaryotic vector.

The recombinant F protein of RSV of the present disclosure is useful for preparing a composition for inducing immune response, which provides immunity or substantial immunity against an infectious agent. Accordingly, in an exemplary embodiment, the present disclosure provides a method for inducing immunity against infection or the symptoms of a disease, which includes a step of administering an effective dose of the recombinant RSV F protein at least once.

In another exemplary embodiment, the present disclosure provides a method for inducing substantial immunity against infection or the symptoms of a disease, which includes a step of administering an effective dose of the recombinant RSV F protein at least once.

The composition of the present disclosure may induce substantial immunity when administered to a vertebrate (e.g., human).

Production of RSV F Gene-Introduced Recombinant Baculovirus

The expression product encoded by the nucleic acid of the present disclosure may be produced by being cloned into a recombinant viral vector.

The recombinant viral vector may be, for example, a phage, a plasmid, a virus or a retroviral vector. Specifically, a viral vector may be used.

In an exemplary embodiment, the vector may be a recombinant baculoviral vector. The construct and/or vector encoding the gene should be operably linked to an appropriate promoter such as the AcMNPV polyhedrin promoter (or other baculovirus), phage lambda (PL) promoter, E. coli lac, phoA and tac promoter. Specifically, it may be overexpressed by the polyhedrin promoter.

The expression construct will further include sites for initiation and termination of transcription and, in the transcribed region, a ribosome-binding site for translation. The coding portion of the transcript expressed by the construct will specifically include a translation initiation codon at the beginning and a termination codon appropriately positioned at the end of the polypeptide to be translated. The expression vector will specifically include at least one selectable marker. The marker includes dihydrofolate reductase, G418 or neomycin resistance gene for eukaryotic cell culture, and tetracycline, kanamycin or ampicillin resistance gene for culture of E. coli and other bacteria. Specifically, the vector may be one or more viral vector selected from a group consisting of baculovirus (e.g., Autographa californica nucleopolyhedrovirus), adenovirus (e.g., canine adenovirus), hepadnavirus (e.g., avihepadnavirus), vacciniavirus (e.g., modified vaccinia Ankara virus) and parvovirus (e.g., autonomous parvovirus). The baculovirus may include Autographa californica nucleopolyhedrovirus or a modified virus strain thereof, and Bombyx mori nucleopolyhedrovirus or a modified virus strain thereof. Also, a bacterial vector may be used. Exemplary bacterial vectors include pQE70, pQE60 and pQE-9, pBluescript vectors, and Phagescript vectors, pNH8A, pNH16a, pNH18A, pNH46A, ptrc99a, pKK223-3, pKK233-3, pDR540 and pRIT5. Eukaryotic vectors may include pFastBac1 pWINEO, pSV2CAT, pOG44, pXT1, pSG, pSVK3, pBPV, pMSG, pSVL, etc.

The recombinant vector described above may be used for transfection, infection or transformation, and may express proteins in eukaryotic cells and/or prokaryotic cells. Eukaryotic host cells may include yeast, insect, avian, plant, Caenorhabditis elegans (or nematode) and mammal host cells. Non-limiting examples of insect cells are Spodoptera frugiperda (Sf) cells such as Sf9 and Sf21, Trichoplusia ni cells such as High Five cells, and Drosophila S2 cells. Examples of fungal (including yeast) host cells include S. cerevisiae, Kluyveromyces lactis (K. lactis), C. albicans, C. glabrata, Aspergillus nidulans, Schizosaccharomyces pombe (S. pombe), Pichia pastoris and Yarrowia lipolytica. Examples of mammalian cells are 293 cells (human embryonic kidney lineage), CHO cells (Chinese hamster ovary cell lineage), Vero cells (African green monkey lineage), MRC cells (human lung fibroblast cell lineage) and MDCK cells (Madin-Darby canine kidney cell lineage). African clawed frog (Xenopus laevis) oocytes or other cells of amphibian origin may also be used. Prokaryotic host cells include bacteria cells, e.g., E. coli, Bacillus subtilis (B. subtilis) and mycobacterial cells.

Pharmaceutical or Vaccine Preparation and Administration

In an exemplary embodiment, the present disclosure provides a vaccine or a vaccine composition for preventing RSV, which contains the recombinant fusion protein according to various exemplary embodiments of the present disclosure. Specifically, the RFP-RSV contained in the vaccine composition may be one wherein the post-fusion fusion protein is linked to the polymerization domain or the flagellin protein recombinant D1 domain.

The vaccine may contain an adjuvant. For example, the adjuvants described in Korean Patent Publication No. 10-2011-0112328 may be used without limitation. Specifically, the vaccine of the present disclosure may contain an aluminum adjuvant, more specifically an aluminum hydroxide adjuvant.

The vaccine composition of the present disclosure may contain any pharmaceutical substance which does not cause in itself harmful immune response in a vertebrate to which the composition is administered, and may contain a pharmaceutically acceptable carrier including any appropriate diluent or excipient that can be administered together with the recombinant F protein without excessive toxicity. The term “pharmaceutically acceptable” means being listed in the US Pharmacopeia, European Pharmacopeia or other generally recognized pharmacopoeias for use in vertebrates, more particularly in human. The RSV F antigen of the present disclosure is administered in an effective amount (as defined above) which is sufficient to induce immune response against one or more strain of the RSV virus. The composition may be used as a vaccine and/or immunogenic composition for inducing protective immune response in vertebrate.

In one non-limiting exemplary embodiment, the concentration of the recombinant F protein of RSV contained in the vaccine is at least about 10 μg/mL, about 20 μg/mL, about 30 μg/mL, about 40 μg/mL, about 50 μg/mL, about 60 μg/mL, about 100 μg/mL, about 200 μg/mL, or about 500 μg/mL. In a specific exemplary embodiment, the concentration of the immunogen is from about 10 μg/mL to about 1 mg/mL, from about 20 μg/mL to about 500 μg/mL, from about 30 μg/mL to about 100 μg/mL, or from about 30 μg/mL to about 50 μg/mL. In another exemplary embodiment, the concentration of the immunogen may be 10-200 μg/mL.

The vaccine or immunogen composition of the present disclosure may be administered to an animal to induce immune response against RSV. In an exemplary embodiment, the animal is human. Usually, the administration dosage may be adjusted within the above-described range on the basis of, for example, age, physical condition, body weight, diet, administration time and other clinical factors. Accordingly, the present disclosure includes a method for preparing a vaccine or immunogen composition which induces substantial immunity against infection or at least one symptom thereof in a subject, which includes a step of adding an effective amount of the immunogen. Although it is desired that substantial immunity is induced with a single dose, additional dosages can be administered via the same or different route to achieve the desired effect. For example, in neonates and infants, multiple administrations may be required to elicit sufficient level of immunity. The administration can continue with intervals throughout childhood if it is necessary to maintain sufficient level of protection against infection. In an exemplary embodiment, a method for inducing substantial immunity against viral infection or at least one symptom thereof in a subject includes a step of administering at least one effective dose of the RSV recombinant F protein, or a fragment or an aggregate thereof. The method for administering the vaccine and/or immunogen preparation includes parenteral (e.g., intradermal, intramuscular, intravenous or subcutaneous) administration, epidural administration and mucosal (e.g., intranasal, oral, pulmonary or suppository) administration, although not being limited thereto. In a specific exemplary embodiment, the composition is administered intramuscularly, intravenously, subcutaneously, orally or intradermally. The composition may be administered via any convenient route, for example, by infusion, bolus injection, absorption through epithelial or mucosal linings (e.g., oral, colonic, conjunctival, nasopharyngeal, oropharyngeal, vaginal, urethral, bladder or intestinal mucosa) and may be administered together with another biologically active agent. The administration can be systemic or local. The prophylactic vaccine preparation is administered systemically, e.g., by subcutaneous or intramuscular injection using a needle and a syringe, or a needle-less injection device. Alternatively, the vaccine formulation is administered intranasally as drops, large aerosol particles (greater than about 10 microns) or sprays into the upper respiratory tract. Although any of the above routes of delivery results in immune response, the intranasal administration confers the added benefit of eliciting mucosal immunity at the site of the entry of the virus. In another exemplary embodiment, the vaccine and/or immunogen preparation is administered to target mucosal tissues in order to elicit an immune response at the site of immunization. For example, mucosal tissues such as gut associated lymphoid tissue (GALT) can be targeted for immunization through oral administration of a compositions which contains an immunogenic adjuvant with specific mucosal targeting properties. Additional mucosal tissues can also be targeted, such as nasopharyngeal lymphoid tissue (NALT) and bronchial-associated lymphoid tissue (BALT).

As the preparation method of a vaccine containing the RSV recombinant F protein of the present disclosure, the administration method thereof and the route of administration, those described in Korean Patent Publication No. 10-2011-0112328 may be used without limitation.

The present disclosure may provide a medicine for treating or preventing respiratory syncytial viral infection, which contains the RSV recombinant fusion protein as an antigen.

The present disclosure provides a use of the RSV antigen for preparation of a medicine for preventing RSV infection.

The present disclosure provides a method for inducing immune response against RSV by administering the RSV recombinant respiratory syncytial virus antigen or a vaccine containing the antigen to a subject.

In another exemplary embodiment, the present disclosure provides a pharmaceutical pack or kit containing one or more container filled with one or more ingredient of the vaccine preparation of the present disclosure.

In another exemplary embodiment, the present disclosure provides a method for preparing a vaccine or an antigen composition for inducing immunity against infection or at least one symptom thereof in a mammal, which includes a step of adding an effective dose of RFP-RSV to the preparation. In a specific exemplary embodiment, the infection is RSV infection.

The RFP-RSV of the present disclosure is useful for preparing a composition which induces immune response and provides immunity or substantial immunity against an infectious agent. Accordingly, in an exemplary embodiment, the present disclosure provides a method for inducing immunity against infection or at least one symptom thereof in a subject, which includes a step of administering at least one effective dose of RFP-RSV.

In another exemplary embodiment, the present disclosure provides a method for inducing substantial immunity against RSV viral infection or at least one symptom thereof in a subject by administering at least one effective dose of RFP-RSV.

The composition of the present disclosure may induce substantial immunity in a vertebrate (e.g., human) when administered to the vertebrate. Accordingly, in an exemplary embodiment, the present disclosure provides a method for inducing substantial immunity against RSV viral infection or at least one symptom thereof in a subject, which includes a step of administering at least one effective dose of RFP-RSV.

In another exemplary embodiment, the present disclosure provides the recombinant fusion protein of respiratory syncytial virus of the present disclosure for use as a vaccine for prevention of infection by respiratory syncytial virus.

Advantageous Effects

The present disclosure provides an immunogenic composition for prevention of RSV infection.

The present disclosure may achieve further improved RSV F protein expression in a host cell than the wild-type RSV F protein through recombination of the RSV F protein.

The RSV recombinant F protein of the present disclosure may act as a superior RSV immunogen.

The RSV recombinant F protein of the present disclosure may provide excellent neutralizing antibody titer.

The present disclosure may provide an RSV F protein which is stable and soluble.

The present disclosure may provide an RSV recombinant F protein antigen having excellent safety.

The present disclosure may provide an RSV antigen and a vaccine having high neutralizing antibody titer.

DESCRIPTION OF DRAWINGS

FIG. 1 schematically shows the concept of the present disclosure.

FIG. 2 A) schematically shows foldon linked to the C-terminal of SK-FP4 by a KLSG linker, and B) schematically shows SK_fla linked to the C-terminal of SK-FP4 by a KLGGGS linker.

FIG. 3 schematically shows foldon and SK_fla linked to the C-terminal of SK-FP4. The sequence of linkage is F4-KLSG-foldon-GGGS-flagellin.

FIG. 4 shows the expression of the recombinant F protein of the present disclosure.

FIG. 5 shows a result of purifying the recombinant F protein of the present disclosure.

FIG. 6 shows a result of analyzing FP4 and FP4-foldon and FP4-flagellin fusion proteins by TEM.

FIG. 7 shows a schedule of administration of the recombinant F protein of the present disclosure and blood sampling.

FIG. 8 shows a result of analyzing the soluble post-fusion F protein-specific IgG total antibody titer of mouse antiserum.

FIG. 9 shows a result of analyzing the RSV A2 neutralizing antibody titer of mouse antiserum.

MODE FOR DISCLOSURE

Hereinafter, the present disclosure will be described in detail through examples, etc. in order to help understanding. However, the examples according to the present disclosure may be changed into various other forms and it should not be interpreted that the scope of the present disclosure is limited by the examples. The examples of the present disclosure are provided such that the description of the present disclosure is more complete to those having ordinary knowledge in the art.

1. Preparation of RSV Recombinant F Protein

Preparation of sF Protein

(1) In order to obtain an RSV recombinant F protein which is stable and soluble, wild-type RSV was prepared as follows. It is well known to those skilled in the art that the following mutations are applied to all RSV subtypes including wild-type RSV-A2, RSVB and RSV-A long. The wild-type RSV F protein of RSV-B GenBank Accession No. AEQ63641.1 was mutated.

(2) A transmembrane domain of the wild-type F protein was removed. The wild-type F protein with the transmembrane domain removed was named SK-Seq 1_dTM and was represented by SEQ ID NO 2. Then, the amino acid sequence of the fusion peptide, which corresponds to the positions 137-145 of SEQ ID NO 2, was changed. SK-FP4 of SEQ ID NO 5 (an example of sF protein) was obtained by substituting the amino acid sequence FLGFLLGVG at the positions with NSGNSSGGG.

Preparation of Polymerization Domain Derived from Heterologous Protein

A domain which is derived from a heterologous protein and can help maintenance of the trimer form of the F protein was introduced to the C-terminal of SK-PF4 of SEQ ID NO 1, which is one of sF proteins.

(1) Preparation of Foldon Domain

A foldon domain of the fibritin protein of bacteriophage T4 was prepared.

The domain was represented by SEQ ID NO 23.

(2) Preparation of Recombinant D1 Domain of Flagellin

The flagellin protein is a building block of the flagellar filament and is encoded by the fliC gene. The flagellin protein of Salmonella enterica was used. The flagellin protein which is encoded by the FliC gene possessed by the serotype group D (Dublin) of Salmonella enterica ssp. enterica was used for experiment.

The recombinant D1 domain of flagellin to be fused with FP4 was designed by linking the amino acid sequences 54-176 and 413-454 of the D1 domain of the FliC gene possessed by the serotype group D (Dublin) of Salmonella enterica ssp. enterica with a linker G.

The domain was named SK_fla and was represented by SEQ ID NO 24.

(3) Preparation of Linker

A linker that can be link the domain to the C-terminal of SK-FP4 was prepared.

Foldon was linked to the C-terminal of SK-FP4 with a KLSG linker (see FIG. 2A).

SK_fla was linked to the C-terminal of foldon with a KLGGGS linker (see FIG. 2B). Then, foldon and SK_fla were linked with a GGGS linker (see FIG. 3).

Designing of Recombinant Polymerization Domain-Bound Fusion Protein

A recombinant fusion protein of RSV (RFP-RSV) was designed as follows.

Foldon and/or SK_fla was linked to the sF protein by a linker. As a result, RFP-RSVs having SEQ ID NOS 28-90 were obtained.

Among them, FP4 having SEQ ID NO 5 was designed as follows.

(1) Designing of FP4-Foldon Fusion Protein

Foldon was linked to the C-terminal of FP4 by a KLSG linker (see SEQ ID NO 31).

(2) Designing of FP4-Flagellin Fusion Protein

SK_fla was linked to the C-terminal of FP4 by a KLGGGS linker (see SEQ ID NO 73).

(3) Designing of FP4-Foldon-Flagellin Fusion Protein

After fusing foldon to the C-terminal of FP4 with a KLSG linker, flagellin was fused with a GGGS linker (see SEQ ID NO 52).

2. Production of Recombinant Baculovirus

(1) Preparation of Recombinant Baculovirus

For easy differentiation of the designed recombinant fusion protein, the DNA sequence of a gene encoding the recombinant fusion protein was optimized. A DNA sequence having SEQ ID NO 91, a DNA sequence having SEQ ID NO 92 and a DNA sequence having SEQ ID NO 93 were cloned respectively into the pFastBac™1 transfer vector. Then, recombinant baculovirus (rBV_FP4-foldon, rBV_FP4-flagellin, and rBV_FP4-foldon-flagellin) was prepared using the recombinant pFastBac™1 and the bac-to-bac® baculovirus expression system (Invitrogen).

Table 1 shows the plaque titer of the recombinant baculovirus stocks.

TABLE 1 Recombinant baculovirus P0 titration P1 titration P2 titration rBV_FP4-foldon 8.8 × 10⁵ pfu/ml 5.8 × 10⁷ pfu/ml 1.2 × 10⁷ pfu/ml rBV_FP4-flagellin 3.0 × 10⁶ pfu/ml 3.4 × 10⁷ pfu/ml 1.0 × 10⁷ pfu/ml rBV_FP4-foldon-flagellin 1.1 × 10⁶ pfu/ml 1.1 × 10⁸ pfu/ml 1.6 × 10⁸ pfu/ml

(2) Expression of FP4-Foldon, FP4-Flagellin and FP4-Foldon-Flagellin Fusion Proteins

Sf9 insect cells were cultured at 27° C. using the insect-XPRESS™ medium (Lonza).

When the cell concentration reached 1.5×10⁶ cells/mL, the cells were infected with the recombinant baculovirus expressing the FP4-foldon, FP4-flagellin or FP4-foldon-flagellin fusion protein at MOI of 0.5. On days 3 and 5 after the infection, the expression of the fusion protein in the medium and the cells was analyzed by western blot under reducing condition (detection was made using the mouse monoclonal antibody 2F7). Protein expression was confirmed in both the cells and the medium, and protein degradation was observed with time. The result is shown in FIG. 4.

3. Purification of Protein

(1) Purification of FP4-Foldon Protein

Sf9 cells were cultured in a 1-L spinner flask. When the cell concentration reached 1.5×10⁶ cells/mL, the Sf9 cells were infected with FP4-foldon rBV P1 at MOI of 0.5, and the medium was recovered 3 days later through centrifugation 6000 g for 15 minutes. TMAE anion exchange chromatography was conducted through column equilibration with 50 mM Tris (pH 8). After loading the prepared culture medium into the column, the flow-through sample was recovered. The flow-through sample was buffer-exchanged and concentrated by UF/DF using a buffer (20 mM Tris, 150 mM NaCl, pH 7.4). A Lentil Lectins column was equilibrated by applying a binding buffer (20 mM Tris, 0.5 M NaCl, 1 mM CaCl₂), 1 mM MnCl₂, pH 7.4). After adding 1 mM MnCl₂ and 1 mM CaCl₂), the sample was loaded into the column.

The protein was eluted by flowing an elution buffer (50 mM sodium phosphate, 100 mM NaCl, 0.5 M methyl-D-mannopyranoside, pH 6.8). The recovered sample was buffer-exchanged and concentrated by UF/DF using PBS. 0.1% Tween-80 was added to the finally recovered protein sample.

(2) The FP4-flagellin and FP4-foldon-flagellin proteins were also purified by the same method. But, unlike in (1), TMAE anion exchange chromatography was conducted through column equilibration with 50 mM sodium phosphate (pH 6.7).

The result of protein purification is shown in FIG. 5.

4. Analysis of Protein Structure by Electron Microscopy

The purified protein sample was mounted on a disc and negative staining was performed. The protein was observed with an electronic microscope.

The result is shown in FIG. 6. The soluble FP4 not fused with foldon looked smaller and thinner than the FP4-foldon fusion protein as a whole. The FP4-foldon had a lollipop-like shape.

5. Test of Immunogenicity

(1) Inoculation of FP4-Foldon, FP4-Flagellin and FP4-Foldon-Flagellin Fusion Proteins to Mouse and Gathering of Serum

The purified FP4-foldon, FP4-flagellin or FP4-foldon-flagellin fusion protein and FP4 were formulated with aluminum hydroxide. The prepared formulation was administered 2 times to 6-week-old female Balb/c mouse via IM route at 30 μg/mouse with a 2-week interval. Details are given in Table 2.

TABLE 2 Antigen Aluminum Groups Description content hydroxide content Mouse n Group 1 FP4-foldon 30 μg 200 μg 5 Group 2 FP4-flagellin 30 μg 200 μg 5 Group 3 FP4-foldon-flagellin 30 μg 200 μg 5 Group 4 FP4 30 μg 200 μg 5 Group 5 PBS  0 μg 200 μg 5

(2) Analysis of F Protein-Specific Antibody Titer of Mouse Antiserum

The soluble F-specific IgG antibody titer of mouse antiserum was measured by indirect ELISA. After coating the soluble F protein on the bottom of a 96-well plate, with 200 ng per well, and binding 4-fold serially diluted antiserum, anti-mouse IgG-HRP antibody was bound thereto and OD value was measured after adding TMB substrate. After analyzing the reaction curve for each mouse with a 4-parameter logistic model, EC₅₀ antibody titer and GMT antibody titer for 5 mice were calculated. The EC₅₀ antibody titer and GMT for soluble post-fusion F protein (post-F)-specific IgG are shown in Table 3 and FIG. 8.

TABLE 3 Groups Antigens #1 #2 #3 #4 #5 GMT Group 1 FP4-foldon 3400 1345 2399 3099 3644 2622 Group 2 FP4-flagellin 2264 1752 2413 1922 773 1701 Group 3 FP4-foldon + flagellin 5812 6200 1780 4636 1826 3523 Group 4 FP4 3306 2946 1823 3398 985 2264 Group 5 PBS/alum 72 50 11 130 79 53

As can be seen from Table 3 and FIG. 8, Groups 1 and 3 showed increased total antibody titer as compared to FP4. Group 2 having only flagellin linked showed very low GMT as compared to Group 4 treated with FP4 alone. That is to say, it can be seen from the above result that total antibody titer was increased as the foldon trimerization domain was bound. Through this, it was confirmed that the recombinant fusion protein of the present disclosure can play an important role in all immune responses induced by antigens.

(3) Analysis of RSV Neutralizing Antibody Titer of Fusion Protein Mouse Antiserum

A monolayer of Vero cells was cultured on a 24-well plate and infected with RSV A2 virus that had been pre-incubated with 2-fold serially diluted antiserum. Three days later, the infected cells were fixed and immunostained with palivizumab, and then immunofocus was counted. The number of immunofocus of each group depending on serum dilution factor is shown in Table 4. The average immunofocus of Group 5, which was inoculated with PBS-alum, was 67.6. The serum dilution factor (ND₅₀) at which the immunofocus was half, i.e., 33.8, was defined as neutralizing antibody titer. The focus forming unit and ND₅₀ depending on serum dilution factor are shown in Table 4 and FIG. 9.

TABLE 4 Serum dilution factor Groups Antigens 10 20 40 80 160 320 ND₅₀ Group 1 FP4-foldon 28 37 45 46.5 64.5 68 18 Group 2 FP4-flagellin 20 35.5 45 57 50 60 23 Group 3 FP4-foldon + flagellin 11.5 23 32 46.5 63.5 56.5 47 Group 4 FP4 27.5 35 50.5 55.5 67.5 56.5 18.5 Group 5 PBS/alum 60.5 68 59.5 65 78.5 74 ND

As can be seen from Group 3, the recombinant F protein wherein both foldon and flagellin proteins were linked resulted in remarkably increased neutralizing antibody production. The neutralizing antibody titer ratio of FP4-foldon-flagellin and FP4-foldon was 2.6, which means that the RSV neutralizing antibody titer was increased by 2.6 times through fusion with flagellin.

The neutralizing antibody titer ratio of FP4-foldon-flagellin and FP4-flagellin was 2.04, which means that the RSV neutralizing antibody titer was increased by 2.04 times through fusion with foldon.

INDUSTRIAL APPLICABILITY

The present disclosure may provide a vaccine against respiratory syncytial virus. The present disclosure may also provide a composition for preventing or treating respiratory syncytial virus infection. 

1. A recombinant fusion protein (F protein) of respiratory syncytial virus (RSV), wherein a polymerization domain derived from a heterologous protein is linked at the C-terminal of a fusion protein (F protein) with the transmembrane domain of the wild-type respiratory syncytial virus (RSV) fusion protein (F protein) deleted.
 2. The recombinant fusion protein of respiratory syncytial virus according to claim 1, wherein the fusion protein (F protein) with the transmembrane domain of the wild-type respiratory syncytial virus (RSV) fusion protein (F protein) deleted has SEQ ID NO 2, and further has the FLGFLLGVG sequence at positions 137-145 modified of the amino acid sequence of SEQ ID NO
 2. 3. The recombinant fusion protein of respiratory syncytial virus according to claim 2, wherein the FLGFLLGVG sequence at positions 137-145 is substituted with i) AAGAAAGAG; ii) QNGQNNGSG; iii) NSGNSSGGG; or iv) TLSKKRKRR.
 4. The recombinant fusion protein of respiratory syncytial virus according to claim 1, wherein the fusion protein with the transmembrane domain of the wild-type respiratory syncytial virus (RSV) fusion protein (F protein) deleted is an amino acid sequence selected from SEQ ID NOS 7-22.
 5. The recombinant fusion protein of respiratory syncytial virus according to claim 1, wherein the polymerization domain derived from a heterologous protein is a polypeptide, and the polypeptide is a bacteriophage T4 fibritin foldon domain polypeptide having SEQ ID NO
 23. 6. The recombinant fusion protein of respiratory syncytial virus according to claim 5, wherein the recombinant fusion protein of respiratory syncytial virus further has a recombinant D1 domain polypeptide of the flagellin protein having SEQ ID NO 24 linked to the C-terminal of the bacteriophage T4 fibritin foldon domain polypeptide having SEQ ID NO
 23. 7. The recombinant fusion protein of respiratory syncytial virus according to claim 1, wherein the recombinant fusion protein of respiratory syncytial virus has the N-terminal of the polymerization domain derived from a heterologous protein linked to the C-terminal of the fusion protein (F protein), and the linkage between the fusion protein and the polymerization domain is covalent bonding by a linker.
 8. The recombinant fusion protein of respiratory syncytial virus according to claim 7, wherein the linker is a KLSG linker having an amino acid sequence of KLSG.
 9. The recombinant fusion protein of respiratory syncytial virus according to claim 8, wherein the C-terminal of the KLSG linker is covalently bonded to the N-terminal of the bacteriophage T4 fibritin foldon domain polypeptide having SEQ ID NO
 23. 10. The recombinant fusion protein of respiratory syncytial virus according to claim 9, wherein the recombinant fusion protein of respiratory syncytial virus has an amino acid sequence selected from SEQ ID NOS 28-48.
 11. The recombinant fusion protein of respiratory syncytial virus according to claim 6, wherein the C-terminal of the bacteriophage T4 fibritin foldon domain polypeptide having SEQ ID NO 23 is linked to the recombinant D1 domain polypeptide of the flagellin protein having SEQ ID NO 24 by a GGGS linker having an amino acid sequence of GGGS.
 12. The recombinant fusion protein of respiratory syncytial virus according to claim 7, wherein the recombinant fusion protein of respiratory syncytial virus has the N-terminal of the bacteriophage T4 fibritin foldon domain polypeptide having SEQ ID NO 23 linked to the C-terminal of the fusion protein (F protein) by a KLSG linker, and has the N-terminal of the recombinant D1 domain polypeptide of the flagellin protein having SEQ ID NO 24 linked to the C-terminal of the bacteriophage T4 fibritin foldon domain polypeptide having SEQ ID NO 23 by a GGGS linker.
 13. The recombinant fusion protein of respiratory syncytial virus according to claim 12, wherein the recombinant fusion protein of respiratory syncytial virus has an amino acid sequence selected from SEQ ID NOS 49-69.
 14. A recombinant fusion protein of respiratory syncytial virus, wherein the recombinant D1 domain polypeptide of the flagellin protein having SEQ ID NO 24 is linked at the C-terminal of the fusion protein (F protein) with the transmembrane domain of the wild-type respiratory syncytial virus (RSV) fusion protein (F protein) deleted.
 15. The recombinant fusion protein of respiratory syncytial virus according to claim 14, wherein the fusion protein (F protein) with the transmembrane domain of the wild-type respiratory syncytial virus (RSV) fusion protein (F protein) deleted has an amino acid sequence selected from SEQ ID NOS 3-22.
 16. The recombinant fusion protein of respiratory syncytial virus according to claim 14, wherein the N-terminal of the recombinant D1 domain polypeptide of the flagellin protein having SEQ ID NO 24 is linked to the C-terminal of the fusion protein (F protein), and the linkage between the fusion protein and the recombinant D1 domain polypeptide of the flagellin protein is covalent bonding by a KLGGGS linker.
 17. The recombinant fusion protein of respiratory syncytial virus according to claim 16, wherein the recombinant fusion protein of respiratory syncytial virus has an amino acid sequence selected from SEQ IDS NO 70-90.
 18. A nucleic acid encoding the recombinant fusion protein of respiratory syncytial virus according to claim
 1. 19. A cell or a virus comprising the nucleic acid according to claim
 18. 20. A vaccine composition capable of inducing immune response in a host, comprising the recombinant fusion protein of respiratory syncytial virus according to claim 1 and a pharmaceutically acceptable carrier, wherein the recombinant fusion protein of respiratory syncytial virus comprised in the vaccine composition has a post-fusion F protein linked to a polymerization domain or a recombinant D1 domain of the flagellin protein.
 21. (canceled)
 22. A medicine for treating or preventing respiratory syncytial viral infection, comprising the recombinant fusion protein according to claim 1 as an antigen. 